Safari Books Online is a digital library providing on-demand subscription access to thousands of learning resources.
The RSI was discovered by Welles Wilder in the 1970s. Wilder introduced RSI in his book New Concepts in Technical Trading Systems. In addition to the RSI technique, he introduced several other indicator and oscillator studies, including the Directional Movement Index (DMI). He presented a variety of unprecedented technical measurement strategies, but RSI is among his finest contributions to the field of Technical Analysis. Although it is properly categorized as a momentum oscillator, RSI is typically considered one of the more popular indicator studies available today.
The RSI was devised by Wilder as a means of calculating the change in momentum of price movement as it relates to a predetermined time period. The name Relative Strength Index is slightly misleading, as the RSI does not compare the relative strength of two markets, but rather the internal strength of the price action of an individual issue.